Battery container and method of making same



y 9 6. A J. c. buDDY 2,404,126

BATTERY CONTAINER AND METHOD OF MAKING SAME Fiied Aug. 28, 1941 2 Sheets-Sheet 1 '-Y 55 v a 6 July 16, 1946. J. c. DUDDY I BATTERY CONTAINER AND METHOD OF MAKING SAME 2 Shets-She t: 2"

Filed Aug. 28, 1941 3 mmmmam mm 1 Arrow 5X Patented July 16, 1946 I 'BA'T'r RYoo This invention relates to a battery "container and the method .of making the z-sarne and ha's for its primary object the manufacture at a 310W cost of an improved .light weightbattery econ- .tainer.

While not limited thereto, this invention relates to an improved battery container suitable for .use ;1With aircraft .batteriesi; Because. of .its electrical shielding properties, it :isdesirable to .have a metallic container for, such batteries.

However, such metallic,cont-ainers andparticu larly those made from light iweightmeta'ls .are subject to attackby therelectrolyte 20f theta-ttery.- It has been proposedto :prevent lsuchat- 752,404,126 7 V V V TAINER AND 'METHOD or f 1' G SAME Joseph Charles l lu'ddy, Philadelphia, Baglfassignor I i to The Electric 'Storage Battery Company, Philadelphia, Payaeorporationpf N ewTJ er sey v Application August as, 1941, SerialNo.- 4 8,630

While such anarrangement ZIJIBVBIIESLCOI'IDSlOIl, I

the rubber lining is difficult and expensive to apply and the finished productis.heaviersthan :djesired.

It isaspecific object ofthisinvention ztorpro ed continuous coating of polymerized vinyl resin.

.It is a stilljfurther specific object of this in-" vention to provide a new and improved method for applying to .the inner surface ore, battery container an .acid and ,alkaline resisting, abrasion resisting, high dielectric strength coating at a relatively low cost.

Further objects and advantages of this in vention will appear as the following description proceeds and the features of novelty which characterize this invention will (be set forth .in the claims appended to and 'stormin'gra part :of this specification. V

:For a more complete understanding 01 this invention, referenc fs'hould be had to the cempasnying drawings in which:

'Figure 1 is -a longitudinal sectional view showing the improved battery container of this inven "=.E'ig ure 2 is a view, parti lnseetion andrparti broken away, showing the improved batterycontainer of this invention-applied as an electrical shield fora-naircraft battery.

Referring to the drawings it --will be observed that the-improved battery container of this invention' 'compri-ses 'a metallic container f0. "Iliis container-f0 is preferably die cast-from an aluminum alloy although it may, if desired,-"be *fabricated frbmanal-uminum sheet. While it is preferred to employ aluminum, it Wil1-be under.- stood'that any other metal maybe employed and maybe-lined in accordance with this-inventionto resist corrosion. illowever, since weight is of' importance in mostio'atteries and -particularlyin batteri'eskto be :used with aircraft it is preferred toemploy a lightweight metal such aluminum or'thelikev 5 The light weight -'-meta'ls have proven' to be readily 'corrodible by the electrolyte. Iheiegis therefore provided on the inner surface offthe container 4 0- an intimately bonded continuous coating of material capable of protecting the metal against the corrosive effect of the "battery electrolyte. In accordance with thisdnvention, the lining H is a coating of polymerized vinyl resin and particularly "a coating o'f-a' copolymer of vinyl chloride and vinylacetate. Such *a "coating when applied in accordance with the i process to beset forth "more fully "hereinafter h'as been found to have the requisite acid-and alkali "resistance, abrasion resistance, and dielectric properties, and moreover to be unaffected by expansion and contraction of the container "With' temelements "in "certain applications, the lining "Hf servingt'o "properly insulate the metallic frame.

Referring to .iFig. 2 in more detail, it will be observed that the particular battery illustrated comprises 'theusual elements or electrodes/l2 which are supported on projections [3 provided in the bottom of a casing M which is'made from a suitable acid resisting material, such as 'ihar'd rubber, As is welllknown in the art. thefllements 1'2 .are immersed in ,a-suitableelectrdlite and a plurality of such elements is provided so tainer H] in accordance with the invention'fully'.

as to produce the required battery characteristics. The elements are connected together in groups and the groups are connected to suitable terminal means projecting through the cover 16 for the casing M. The cover is sealed in place by means of a suitable sealing compound 11. v

AfterQJ-the'battery: has been assembled, it is placed themetallic container l0 and a'cove'r I8 is provided to enclose the assembly. Flexible connectors H] are provided for connecting the ter-i minals to the external terminals 29 mounted in the side Wall of the container. A;

I The battery assembly is secured in the con described and claimed in my co'pending applicafcoat applied is one which readily sticks to the cleaned and etched aluminum surface. This prime coat may consistof a resin paint having the following approximate composition by weight: i I

Y 7 Per cent Solvent naphtha; benzine, I xylol, or I ---=tol uo1 a -62 to 6:5 Chlorinated rubber 15 to 18 Pigments consisting substantially of titanium and silica -jiiikprime coat having the above composition has i been found to be unsuitable for spraying, partion, Serial No. 409,443, filed Septe'rri-ber4,"1941, and assigned to the assignee of the present iIit tspmt o t e a own-be we n h d -.W 1

vention. Briefly however the securing means ticularly in a'closely confined space such as the inside of the container 10. However, by'diluting the prime coat and spraying at a relatively high pressure a coating free from stringing may be secures the upper portion of t he; casing. i Both 7 the wax and sealing ,compound are. applied in the 1 liquid state (hot) -;and upon cooling they securely hold the battery inposition. As shown inth awi atm se li comp nd 23 moio he batt y n a the con a tiq ands m .of the wax 2| projects up around the bottom of the battery casing. This combination of Wax and sealing compound has been found tov secure the at ery in the on ainer irr e tire o t t .re a ure :tql i b tte sv s i g ea. o es aline x has send h h irmp a urec fl .act r'is s nd t e. se li c m und g low temperature characteristics. Mqreoyer the W 48" nd Sealing I e n und gnc i n. t9. Pre e le fi. fih fil et ql ha; he n er a of the container.

t r em ht iis a enue ie s'pmid d a new d mp ove b t o e s ri the only method for producing the improved batetrs a s i p F nd ticul l for applying the lining to the inside of the container. Among the factors to be considered in applying the lining or coating l ltdtliebatjfiery container 1 o is ('1') f obtaining a lining" which intimately bonds to the corrodible 'rnetal and not attacked by the electrolyte during the life-9f the battery, and, (2)1' obtaining a material which can be simply and easily applied totheiriner surfacfof the container to form an intimately bonded continuous coating thereon. One of l the salient features of the improved process of this invention is that the lining Il may be" applied .by a spraying opration,thus' permitting the prci .duction of large quantities of such containers and effecting perunit. I The complete process for producing the above described lined'container Willnowb'e described.

The metallic container!!! isjformed,'preferably by die casting it from a suitable aluminum alloy; and after the forming operation is 1 completed,

the casing" is inspected" and thoroughly cleaned cleaned and prepared in this 'manner, a prime 7 coat is applied'to the inner s1urface. The

a substantial saving in the cost accordance with this invention the prime material is diluted with a'solvent of the'class of xylene. toluene or benzine, or'a mixture thereof, in the proportion of ten parts of primeyto' six parts of solvent. -Afterdilution therprime'coat isthoroughly agitated, and this agitation continues throughout the spraying operation.- -'I;'he spraying operation is carried on at the relatively high air pressure of 80 to 100 pounds per square inch and 'at'a paint pressure of2 to 5 pounds per square inch, After spraying, the prime coat is air dried until practically all the liquids therein have been evaporated.

Following therprim coat an intermediate coat is applied so .as toform a bond or adhesive between the prime coat and succeeding coats of The vehicle may consist of approximately butylacetate and of 40% methyli'sobutyl ketone. The pigment is'made up largely of silica (sand)", titanium oxide, lithopone and'graphite. When suspended in solution theps'ilica. is presentf fin. V I about 25% by "volume. This amount of silica ives body to the finished jcoat and presents a surface roughness desirable for good adhesion" of succeedingcoats. I V ,1 'L j To the composition'set forth abovexis added a plasticizer such as dibutyl phthalate in the amount of 60, c.c.s per gallon'of solution. This plasticizer has been found to keep the film soft and pliable and adds to the lasting adhesion thereof. v j w The intermediate coat is likewise applied bya spraying operation. Since an enamel relatively high in vinyl solids is being sprayed, it is neces sary to apply a wet coat. In'other words itis a necessary to have a heavy flow of material, yet

not so heavy as tocause runs of'Sa'ggingof-such a relatively dense material. It has been found that if the material flow is too light or the air' pressure toohigh, a blowing or solidifying action of the vinyl solids occurs in the spray due to'the confined space in which; the spraying. operation 7 r. qfist n henqmen n..li s beenrpu ia to. circus most along the bottom edge of the inner side walls-of the container, andparticularly the side wall first sprayed. It has been found that by employing anair pressure of approximately :40 pounds per. square inch and a paint pressure of approximately 15 pounds per square inch, an intermediate coat having the composition set forth above may be sprayed into the confined space with blow.greatly'minimized or substantially eliminated. 1

After spraying, theenamel coat is preferably permitted 'to'dry thoroughly in :air but, if desired, succeeding coats may be applied before the enamel has dried. v Up to this pointin the process, the lining on theinside surface of the casing has relatively poor insulation'resistance and is not acid proof. The two coatsapplied, the prime coat and the intermediate or enamel coat, have as their principal' purpose the presenting of a surface on which it is possible to spray and have adhere satisfactorily one or more seal coats consisting substantially of a solution of a copolymer of vinyl chloride and vinyl acetate in a suitable solvent without the use of a high temperature bake which is characteristic of successful adhesions of Vinylite coatings when applied totbare metal. The adhesion of the seal coats described below is probably due to two conditions. First, the binderin the intermediate or enamel coat consistsof vinyl solidsan'd, .of course, one vinyl solid will stick'to the other. Second, the filler in :the enamel coat is silica or sand which presents 3.3, roughened surface which is desirable fnom'ttheadhesion standpoint.

.lSince the prime coat is not inert and since the intermediate coat is porous the combinationdoes not have the requisite dielectric and acid resisting properties. It is therefore necessary to cover this combination with a material which will adhere thereto, will have the ability to resist attack by the electrolyte of the battery, and will have high dielectric strength. As mentioned above a copolymer of vinyl chloride and vinyl acetate dissolved in a suitable solvent has been found to be such a material.

Since high dielectric strength or the ability to resist voltage break down is a desirable property of the finished lining, the more vinyl solids that can be incorporated in the composition of the seal coats, the greatepwill be the covering power and the thicker will be the film for a. given coat. Because of this it is desirable to incorporate as much dissolved vinyl solids as possible in the seal solutions without exceeding a figure of viscosity that is prohibitive from a spray standpoint.

A further factor which must be considered in the composition of the seal'coat is the character of the solvent employed. If solvents are used which have high evaporation rates, entrapped air (bubbles) in the wet film is not released and the resulting film is porous.

compounds employed, it has been found that spraying can be accomplished at a. low pressure, and since the film does not set up so readily, any entrapped air in the film escapes, thus producing a substantially continuous surface free from pin holes.

A further factor to be considered in the application of the seal coat is its ability to be sprayed inside the container where all of the air shot into the space is ejected into the atmosphere.

If a solvent having a lower evaporation rate is used, assuming thatthe substance is a good solvent for the Vinyl v Per cent Vinyl solids 1 14-17 Approximately dibutyl-phthalate 3.5

Mesityl' oxide 19.5 825 Mesityl oxide is the 'preferredsolvent. However, a solvent mixture consisting of approximately 54% butyl acetate and 29% methyl isobu'ty ketone, parts by weight,'maybe used.

As explained above, this material is sprayedat a relativelylow air pressure andthe flow of :material is relatively heavy was to eliminate fog :or blow. It has been found that an air pressure of 20 to 40 pounds per square inch and a paint pressure of 15 to 20 pounds per square inch permits satisfactory spraying of this material in the confined space. 7 qt After spraying, the first seal coat is permitted to dry for about 5 to 10 minutes in 'airiand then .a'second seal coat having .the following'composie tion. by weight is applied. n l

Vinyl solids; 22 Dibutyl phthalate {415 Carbon black .75

Mesityl' oxide 72175 an air pressure of about 30-40 pounds per square inch and a paint pressure of about 30 pounds per square inch. After the first coat of this material has been applied, the container is permitted to dry in air for five to ten minutes. A second seal coat of this material is then applied in the afore-described manner, thus making three seal coats in all. The air dry between successive seal coats functions to give each applied coat sufficient set to prevent runs or sags in the film. It will be understood however that this brief drying period does not produce complete drying and hence the succeeding coats are applied while the preceding coats are still wet.

After the last seal coat has been applied, the container is permitted to air dry until it is touchproof. This requires from eight to twenty-four hours. Subsequent to this air dry the container is baked at a temperature of approximately 200 F., for 1 /2 to 2 hours. That is what may be called a low temperature bake, and its function is to rid the coating of any excess solvent. The temperature employed is below the boiling point of the solvent and thus some solvent is retained. This retained solvent acts as a plasticizer and imparts abrasion resistance and toughness to the coating. Moreover, it has been found that the small amount of solvent retained does not adversely affect the dielectric properties of the coating.

With the final low temperature bake the process of lining the container is completed, and in order to test its dielectric properties it is filled Percent 7 7 withan acid electrolyte or an aqueous solution of awetting agent and subjected to a voltage stress of 500 voltsA. C. Any breaks or discontinuities in the lining will be detected by such a test. a v

By following the foregoing. process it has been found that an intimately bonded continuous lin-' ing of a polymerized vinyl resin is provided 'on the interior surface of a battery container made from a corrodible metal. ,This lining forms an acid and alkaliwresisting, abrasion resisting, high dielectric strength coating which is unaffected by i the expansion and contraction of the metallic casing with temperature. Thus there is provided in accordance with thisinvention a light weight batterycontainer, having aftough, long life, acid resisting lining which is capable of initially withstanding a voltage'stress of at least -500 volts A. C. 1 I

. 1,While this invention has been 'set forth in detail, it will be understood that modifications maybe made therein, and it is intended in the appended claims to cover all such modifications as come within the true spirit and scope-of this invention.

I. claim:

1. A light weight battery container comprising an .aluminumcontainer, the inner surface of which is provided with an acid and alkali resisting,. abrasion resisting continuous coating which issufliciently flexible to withstand the expansion j and contraction of said aluminum container'with temperature and is capable of withstanding an initial voltage stress of at least 500 volts A. 0.,

I said coating comprising a prime coat of a ch1orinateid'rubb'er base resin paint having the property of adhering to the surface of said aluminum container, an enamel coat including a substantial amount of silica bonded to said prime coat, and

a seal coat of a copolymer of vinyl chloride and vinyl acetate firmly adhering to said enamel coat.

2. The method of providing an intimately bonded continuous acid-resisting lining of high dielectric strength on the interior surface of .a

metallic container which includes the steps of treating said surface to remove undesirable films, applying a prime coat of a chlorinated rubber base resin paint, air drying to remove the solvents, then applying to said'pr'ime coat an 7 intermediate enamel coat comprising a vehicle of butyl acetate and methyl-isobutyl ketone, in which is suspended vinyl solids and a pigment in cluding silica and titanium oxide. to which is added aplasticizer, applying to this intermediate coat a layer comprising asolution of a copolymer of vinyl chloride. and vinyl acetate in a suitable solvent, allowing this final layer to air-dry until touch-proof, and then baking at a temperature below the boiling point of the solvent to retain a small proportion of the solvent.

3. The method of providing an intimately bonded continuous acid-resisting liningof high dielectric strength on ari inner surface ,of a metallic container which includes the step of treating said surface to remove undesirable films; applying a prime coat of a chlorinated rubber base resin paint, air drying toremove the sol- 

